JPH1083978A - Method and device for mounting semiconductor wafer on polishing block - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to use water-based adhesive agent without adverse effects on the flatness of a semiconductor wafer, by applying the water-based adhesive agent on the surface of a polishing block, and heating the wafer by radiation using a radiation heater in a dry environment, thereby drying the water-based adhesive agent quickly and softening the wafer at the low cost. SOLUTION: A door 26 is lifted, and a polishing block B having the coating of water-based adhesive agent, which is applied on the upper surface, is arranged on a holder. The door 26 is closed, a lamp unit is operated and infrared-ray energy is radiated upward toward the bottom surface of the block B from a heater. Here, when the specified temperature sufficient for softening the water- based adhesive agent is detected with a pyrometer, the lamp unit is stopped, the door 26 is lifted and the block B is removed from the holder. At this time, it is recommendable that the lamp unit is stopped when the pyrometer has detected 75 deg.C. In this way, the semiconductor water is bonded to the softened adhesive agent after the water-based adhesive agent has been softened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates generally to a method and apparatus for attaching a semiconductor wafer to a polishing (polishing) block and holding the wafer during polishing.
In particular, the present invention relates to an infrared heater for heating a polishing block to soften an adhesive applied to the polishing block so that the wafer is temporarily bonded to the polishing block.

[0002]

2. Description of the Related Art Both sides of a semiconductor wafer are polished during its manufacture to provide a very smooth finish and surface flatness. Semiconductor wafers must be polished to be very flat and smooth before printing electrical circuits on the wafer by electron beam lithography or photolithography. Flatness is important to maintain print line resolution of 1 micron or less. However, since the wafer is thin, it may bend during polishing and may not have the required surface flatness and finish if not firmly supported across the wafer. Therefore, it is important that the wafer be supported throughout its area during polishing.

[0003] To prepare a wafer for polishing, the wafer is mounted on a flat polishing block using an adhesive or wax, which adhesive or wax firmly grips and accurately supports the wafer. The adhesive is applied to one side of the polishing block in a thin film, and the block and the adhesive are heated so that the adhesive dries and softens. The wafer is pressed against the softened adhesive, which holds the wafer firmly as it cools, so that the wafer is not easily pulled or stripped from the block during the polishing process . Also, the adhesive solidifies as it cools, so that the adhesive firmly supports the wafer during the polishing process and provides the required surface flatness and finish.

[0004]

Conventionally, an apparatus known as a steam pot has been used to heat a polishing block to which an adhesive has been applied. As the name implies, a steam pot is a container for boiling water. To heat the block, the block is placed in an opening at the top of the steam pot such that the side of the block opposite the adhesive is exposed to the vapor in the container. The steam heats the block by convection and heat transfer. The block conducts heat from the exposed side to the side to which the adhesive is applied, thereby drying and softening the adhesive. However, since the block is cooler than the steam, water condenses on the side exposed to the steam. Since the side of the block with the adhesive does not face the interior of the steam pot, water occasionally contacts the adhesive. When the wafer comes into contact with the adhesive, a small mark is formed on the adhesive, whereby certain portions of the small wafer are improperly held and supported. As a result, if the polishing block is heated in a steam pot and water condenses or bounces on the block, the polishing block must be dried before further processing to prevent water from contacting the adhesive. .

Conventionally, an adhesive containing trichloroethylene as a solvent has been often used. However, it has been found that trichlorethylene can have an adverse effect on the environment, so other adhesives that do not contain trichlorethylene have been introduced. For example, water-based adhesives have been developed. However, these "green" waterborne adhesives are very dispersible in water and do not perform well when heated in a steam pot. Thus, when water droplets come into contact with the adhesive, large voids are created and the wafer is not properly supported or held.

[0006] In one attempt to reduce water bounce,
The amount of power supplied to the steam pot was reduced, which reduced the amount of steam produced and increased the time to sufficiently heat the block. Long heating times are undesirable because they increase production time and costs. To speed up manufacturing, softer adhesives have been used so that the blocks do not have to be heated to high temperatures. This allows lower power settings and shorter heating times to be used. However, the soft adhesive is sticky, so it is not easy to release the wafer after polishing,
This offsets the manufacturing advantages obtained with soft adhesives.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and apparatus for heating a polishing block to dry and soften an adhesive quickly and inexpensively, and to improve the flatness and surface finish of a semiconductor wafer. It is to provide a method and apparatus in which a water-based adhesive is used without adverse effects, and a method and apparatus in which a polishing block, a semiconductor wafer and an adhesive do not come into contact with water.

The method of the present invention is used to mount a semiconductor wafer on a polishing block to hold the semiconductor wafer during polishing. In general, the method provides a polishing block having a surface for mounting a semiconductor wafer, applying an adhesive to the polishing block surface,
Radiating the polishing block and the adhesive to soften the adhesive, and bonding the semiconductor wafer to the softened adhesive. The step of radiatively heating the polishing block and the adhesive is performed by a radiant heater in a dry environment.

In another aspect, the invention is an apparatus for accomplishing the above-described process of heating a polishing block and an adhesive to soften the adhesive. In general, the device is
A polishing block holder configured to receive and hold a polishing block; and a radiant heater that pours heat radiation energy toward the polishing block received and held by the polishing block holder to heat the polishing block. Have.

[0010] In another embodiment of the present invention, a semiconductor wafer mounting apparatus includes: an adhesive application apparatus; a radiant heater;
It has a mounting device and a controller. The adhesive application device applies a release adhesive to one surface of the polishing block. The radiant heater applies heat radiation energy to the polishing block to which the adhesive has been applied to heat the polishing block and the adhesive. The mounting device places one surface of the semiconductor wafer on the polishing block surface. The controller controls the operation of the adhesive application device, the radiation heater, and the mounting device.

Other objects and features of the invention will in part be obvious and will in part be pointed out hereinafter.

[0012]

DETAILED DESCRIPTION OF THE INVENTION Referring first to the drawings and first to FIG. 1, an apparatus for heating a polishing block according to a first preferred embodiment comprises:
The whole is indicated by reference numeral 20. The device 20 supported on the frame 22 has a vertical member 22a and a horizontal member 22b. The frame includes a front panel 24a, a rear panel 24b, a side panel 24c, and a top panel 24.
d, and supports a sliding door 26, which can be opened to put the polishing block B in and out of the device. Control panel 28 includes instruments for monitoring and controlling the operation of the device. The apparatus 20 includes a polishing block holder generally indicated by reference numeral 30 (FIG. 6) and an infrared heater generally indicated by reference numeral 32 (FIGS. 2 and 3). The holder 30 and the heater 32 are provided below the table 34. The table has an opening 36 sized to receive the polishing block B. As described in detail below, the holder 30 of the first embodiment is formed by a round protrusion of a cooling water pipe extending to an opening 36 below the table 34.

FIGS. 2 and 3 show an apparatus having panels 24a-24d, a sliding door 26 and a control panel 28. FIG. The control panel has been removed from frame 22 so that internal components such as heater 32 are visible. The internal structure of the infrared heater 32 will become more apparent with reference to FIGS. The heater includes a housing 40 that houses three parallel arranged infrared lamp units indicated generally by the reference numeral 42. Each lamp unit 42 includes a main body 44 and four insulators 46 on the bottom of the housing 40 separating the main body from the housing to electrically insulate the lamp unit. Disposed near the end of each body 44 are five hollow supports 50.
These support an annular infrared emitter or lamp 52 near a reflective groove 54 (FIG. 9) formed on the top surface of the body.

The lamp unit 42 is disposed below the holder 30 so as to extend from the front to the rear in the housing 40 to the lamp 52. Five lamps 52 are provided on the support 50 of the central lamp unit 42, but only three lamps are provided on another unit. Since the lamp furthest from the holder does not efficiently heat the block B held in the holder, three lamps 52 are located on the support 50 closest to the holder 30. Each lamp 52 has a wire lead 54,
It extends downwardly from the end of the lamp via the hollow support 50 and reaches a common bus 56 provided near the bottom of the support. The bus 56 is connected to an external power supply (not shown) controlled by a programmable logic controller 58b (FIG. 12) provided outside the device. The lamps 52 are each supplied with 480 volts and 60 amps of current to obtain 6 kilowatts of power. In the most preferred embodiment, the lamp unit 42 is a model 509 manufactured by Research, Minneapolis, MN.
0-10-01 high-density infrared heater parts, lamp 52
Is Q6MT3 / CL / HT manufactured by Research
It is a quartz type infrared emitter. However, other types of radiant heater lamp units and lamps can be used without departing from the scope of the present invention.

Each body 44 has two grooved ports 60 (FIG. 8) on its lower side. As shown in FIGS. 9 and 10, each body 44 has a cooling passage 62 connected thereto. These cooling passages extend through the body from one port to the other. The cooling water is conveyed to the rear port of the right unit 42 as shown in FIG. Right unit 42
The cooling water sent to the rear port 60a is conveyed through the passage 62 of the right unit, exits the front port of the unit, and proceeds there via the tube 64 to the front unit of the central unit. Similarly, water exits the rear port before passing through the central unit and through the second tube 65. A second tube connects the center unit and the rear port of the left unit. Water is conveyed through the left unit and exits through rear port 60b. Thus, water entering the first unit is sent to the second unit and transported from the second unit to the third unit.
The short nipple 66 (see also FIG. 9)
0, the front left and rear right ports 60a, 60b extend through the housing 40 from these ports for connection to the cooling water circuit.

Air is introduced into the housing 40 through two holes (only one is partially shown in FIG. 8) in the bottom of the housing. Air passes between the unit 42 and the bottom of the housing and the hollow lamp support 50 near the end of the unit.
Go to The air moves upward through the support 50 and toward the center of each unit 42, where a plurality of tubes 72 disposed centrally along the unit allow air to move downward through the tubes 72. Into a plenum (not shown) attached to the bottom of the housing 40. Returning to FIGS. 2 and 3, the exhaust tube 74 exhausts the hot air from the plenum to an exhaust facility (not shown) located outside the apparatus 20. The exhaust system includes a blower for sucking air through the housing 40 and discharging the air from the exhaust tube 74 to cool the heater 32. As will be described in detail below, a flow sensor (not shown) is provided in the exhaust tube 74 to measure the air flow drawn through the tube so that the heater 32 shuts down if the cooling flow is insufficient. Are located.

The cooling system for table 34 and holder 30 is shown to include a cooling water manifold 80. This manifold is provided on the right side of the frame 22 and distributes cooling water from a supply line 82 (FIG. 3) connected to the rear end of the manifold to flexible cooling water lines 84a-84e connected to the upper part of the manifold. The supply line 82 is used to supply cooling water to the manifold 80.
It is connected to an external cooling water source (not shown). A solenoid valve 86 and a flow sensor 88 are located on the supply line 82 to control and monitor the amount of water to the heater 32 and other cooling passages. The line 84 a extends to the nipple 66 associated with the rear right port 60 shown in FIG. 8 and sends cooling water to the lamp unit cooling passage 62.

Lines 84b-84d extend to upper and lower cooling plates 100, 102 (FIG. 4) located below table 34. As shown in FIG.
Consists of a 1/16 inch thick plate of stainless steel. Two 1/4 inch thick aluminum plates are 1/4
The cooling plates 100 and 102 disposed below the table 34 are formed at intervals of inches. As shown in FIGS. 5 and 6, two portions 104, 106 of the copper tubing are located between the upper and lower cooling plates 100, 102 and a portion 108 of the stainless steel tubing is located below the lower cooling plate. I have. The piping portions 104 and 106 are formed in a winding cooling passage for cooling the table 34. Lines 84b and 84c (FIGS. 2 and 3) extend from manifold 80 and deliver cooling water to piping sections 104 and 106, respectively. As shown in FIG. 6, the stainless steel pipe portion 108 is formed with a round protrusion 110 protruding inward from the table opening 36. Further, the round protrusion 110 forms the block holder 30 of the first embodiment. A line 84d (FIGS. 2, 3) extending from the manifold 80 is connected to a stainless steel tubing section 108 for sending water to the holder 30 to cool it.

FIG. 7 shows the frame 22 around the heater 32.
4 shows four plates 112 and tubes 112 provided one by one in the vicinity of each side surface of the housing 40. These plates 112
Are omitted in FIGS. 2 and 3 for clarity. The cooling water is sent to the tube 114 via the line 84e. The tube 114 is separated from the plate 112 by the tube 11.
It has a serpentine shape to facilitate the transfer of heat to the cooling water transported through 4. Device 20
After moving along one side, the water travels to similar tubes and plates near the side of the device and travels around all four sides.

Returning to FIGS. 2 and 3, disposed on the left side of the frame 22 is a cooling water return manifold 120 similar to the manifold 80. Return manifold 1
Numeral 20 guides cooling water from five inlet ports 121 (only one of which is shown in FIG. 2) at the top of the manifold to an outlet port (not shown) at the rear end of the manifold. The drain line 122 is connected between an outlet port of the manifold 120 and an external drain facility (not shown). Five flexible cooling water outlet lines 124a-124e are connected to respective manifold inlet ports 121. A line 124a extends from the nipple 66 associated with the front left port 60 of the heater 32 shown in FIG. 8 to deliver used cooling water to a drain. Lines 124b-124
e is connected to the downstream ends of the pipe sections 104, 106, 108 and 114, respectively, and drains the used cooling water from those passages.

The second solenoid valve 130 disposed above the first solenoid valve 86 is connected to the controller 58.
The door 26 (FIG. 1) is opened and closed in response to a signal from b (FIG. 12). The valve 130 is connected to a linear actuator 132 (FIG. 1) and supplies air to the actuator to press its piston downward. The piston is connected to a wire 134 (FIG. 1) connected to the sliding door 26 (FIG. 1), and the door is raised when air is sent to the actuator 132.

As shown in FIG. 1-3, in order to detect the presence of the polishing block B in the holder, a proximity switch 14 is attached to a table 34 near the polishing block holder 30.
0 is provided. Switch 140 is connected to programmable logic controller 58b (FIG. 12). An optical pyrometer 142 (FIGS. 2, 3) is provided near the top of the apparatus 20 and is directed at the holder to detect the temperature of the top of the polishing block B held in the holder 30. The pyrometer 142 is also connected to a programmable logic controller.

In operation, the door 26 is raised and a polishing block B having an adhesive coating applied to its upper surface is placed on the holder 30. The door 26 is closed, the lamp unit 42 operates, and infrared heat energy is emitted upward from the heater 32 toward the bottom surface of the block B. When a predetermined temperature sufficient to soften the adhesive is detected by the pyrometer 142, the lamp unit 42 stops, the door 26 rises, and the block B is removed from the holder 30. Other temperatures fall within the scope of the present invention, but the pyrometer 142
It is preferable to stop the lamp unit 42 when the temperature is detected. The reason for this is that the temperature of the top of the block and the adhesive continue to increase even after the lamp unit is stopped due to the continuous heat transfer to the top of the block caused by the high temperature gradient in the block. When the upper portion of the block reaches 75 ° C. and the lamp unit 42 stops, the lamp unit 42 is stopped before the wafer is bonded (about 30−30 seconds after the lamp unit 42 stops).
At 35 seconds), the top of the block and the adhesive will reach 95-100 ° C. A radial hole (not shown) on the side of the block B allows the insertion of a handle for transporting the heated block.

Programmable logic controller 58b
(FIG. 12) shows that the lamp unit 4 is provided if sufficient cooling water or cooling air is not detected by the flow sensor in the water / air passage.
2 is programmed not to work. Also, if proximity switch 142 does not detect the presence of block B in holder 30, lamp unit 42 will not operate. A sensor (not shown) is also connected to door 26 to detect if it is completely closed. Door 2
Even if 6 is partially released, the controller 58b does not operate the lamp unit 42. If the lamp unit 42 does not operate for a predetermined time (for example, 15 seconds), closing the solenoid valve 86 will cause the controller 58b to stop the cooling water.

In the second embodiment shown in FIG.
0 'has a heater supported on the polishing block holder 30'. The heater 32 'has an opening (not shown) facing downward toward the holder 30'. Holder 3
0 'has three ceramic legs 152 on which the polishing block B is seated. Legs 152 are used to prevent heat transfer from block B to holder 30 '. The holder 30 'is provided on a bearing 154, and is driven by a motor 156 to rotate the holder with respect to a frame 158 provided below the heater 32', thereby reducing a circumferential thermal gradient around the block B.

The frame 158 is provided on a vertical rail 160 which raises or lowers the frame to position the polishing block B near the heater 32 '. The holder 30 'of the second embodiment is hollow so that the optical pyrometer 162 can aim at the bottom of the block B and determine its temperature. Otherwise, the device 20 ′ of the second embodiment
Is the same as the device 20 of the first embodiment.

FIG. 12 shows a semiconductor mounting device 170, which has the radiant heater device 20 described above. The device 170 also includes a polishing block B before being transferred to the heater device 20.
Has an adhesive application device 172 for applying an adhesive to the surface of the device. When the heater device 20 has sufficiently heated the adhesive and the block B, the semiconductor wafer mounting device 174 is used to place the semiconductor wafer on the polishing block B. The controllers 58a to 58c control the operations of the adhesive application device 172, the radiation heater device 20, and the mounting device 174, respectively. In another embodiment, a single controller may be used to control the overall system 170. For example, the radiant heaters 32, 32 'of this embodiment can be configured as described in U.S. patent application Ser. No. 08 / 242,560.
It may be incorporated into automatic wafer mounting and polishing equipment. The radiant heaters 32 and 32 'are described in the above-mentioned application No. 08 / 242,56.
It is replaced with the steam pot disclosed in No. 0.

[0028] A number of alternative embodiments of the device described above can be envisaged without departing from the scope of the invention. For example, a transport mechanism may be added to transport the block B toward and from the holders 30 and 30 '. Further, instead of stopping the heater after reaching a predetermined temperature, the heater may be stopped after a predetermined time has elapsed by using a timer control circuit instead of the pyrometer control circuit.

[0029]

From the foregoing, it will be appreciated that certain objects of the invention have been attained and other advantages have been obtained. The apparatus 20 described above heats the polishing block B without contacting the water, so that the adhesive does not become small marks during heating. As a result, an aqueous adhesive can be used without damaging the adhesive surface. Further, according to the apparatus of the present invention, there is no need to dry the block when heating it. Thus, the drying step is eliminated from the manufacturing process.

Although the present invention has been described with reference to particular embodiments, it is to be understood that the invention may be modified and varied without departing from the scope of the invention as defined in the following claims. is there.

[Brief description of the drawings]

FIG. 1 is a right front perspective view of a heat-dissipation type polishing block heater according to the present invention.

FIG. 2 is a front view of the polishing block heater with a panel removed to show the internal structure.

FIG. 3 is a right side view of the polishing block heater of FIG. 2;

FIG. 4 is a partial schematic cross-sectional view of a cooling water passage obtained along a line 4-4 in FIG. 1;

FIG. 5 is a schematic plan view of an upper cooling water passage.

FIG. 6 is a schematic top view of a lower cooling water passage.

FIG. 7 is a schematic right side view of a cooling water passage adjacent to the right side of the infrared heater.

FIG. 8 is a partial bottom view of the infrared heater according to the present invention.

FIG. 9 is a partial front view of the infrared heater.

FIG. 10 is a partial right side view of the infrared heater.

FIG. 11 is a front view of a polishing block heater according to a second preferred embodiment of the present invention.

FIG. 12 is a block diagram showing a semiconductor mounting device according to the present invention.

[Explanation of symbols]

B: Polishing block, 20: Device, 30: Holder, 32:
Infrared heater, 42: lamp unit, 44: body, 5
2 ... lamp.

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Harold E. Hall Jr. United States 27572 Rougemont, North Carolina, Highway 157 West 8617

Claims (10)

[Claims] 1. A method of placing a semiconductor wafer on a polishing block and holding the semiconductor wafer during polishing,
In the above method, a polishing block having a surface on which a semiconductor wafer is placed is prepared, an adhesive is applied to one surface of the polishing block, and radiant heat is applied to the polishing block and the adhesive in a dry environment by a radiant heater to bond the polishing block. Softening the adhesive, attaching the semiconductor wafer to the softened adhesive,
Process. 2. The method of claim 1, wherein the step of applying radiant heat includes directing a radiant heater to a polishing block surface opposite the adhesive. 3. The method of claim 2, further comprising the step of detecting a temperature of the adhesive and terminating the application of the radiant heat when the temperature reaches a predetermined limit. 4. The method of claim 3, wherein the step of providing radiant heat ends when the temperature of the adhesive reaches about 70 ° C. 5. The method of claim 3, wherein the step of providing heat of irradiation ends when the temperature of the adhesive reaches at least about 100 ° C. 6. The method of claim 1, comprising terminating the application of the radiant heat after a predetermined time period of about 60 seconds or less. 7. The method of claim 1, wherein the step of applying radiant heat includes the step of applying radiant heat from a radiant heater to a surface of the polishing block having the adhesive. 8. The method of claim 1, comprising detecting the presence or absence of the polishing block and delaying the step of applying radiant heat until the polishing block is detected. 9. An apparatus for releasably bonding a semiconductor wafer to a polishing block for heating the polishing block to soften an adhesive applied to the block so as to securely hold the semiconductor wafer during polishing. Wherein the apparatus comprises: a polishing block holder configured to receive and hold the polishing block; and a radiator provided on the apparatus, wherein the polishing block is received and held by the polishing block holder. A radiant heater for directing thermal energy toward the polishing block. 10. The apparatus of claim 9, wherein said radiant heater comprises an infrared heater having an infrared heater member oriented to direct radiant heat energy to said polishing block holder.